Working with Vectors
by Lea Rosema
Three.js provides several classes for vector arithmetics. One thing to keep in mind is that the methods like add modify the current object instance and won't create a new instance.
// Initialization:
const a = new THREE.Vector2(1, 2);
const b = new THREE.Vector3(2, 2);
const c = new THREE.Vector2(); // default constructor arguments are (0, 0)
// d = a + b;
const d = new THREE.Vector2();
d.copy(a); // copy the values of a into d
d.add(b); // add b to d
const cd = c.distanceTo(d);
// Important to note:
// add mutates the values of the current vector